METHOD OF TREATING HEAVY METALS CONTAINING MEDIA SO AS TO REMOVE SUCH METALS, IN PARTICULAR CHROMIUM

摘要

1. A method of purifying media containing heavy metals, with dominant amounts of chromium and/or iron and/or zinc and/or cadmium and/or nickel. It consists in precipitating the metals in the form of a poorly-soluble deposit of heavy metal compounds, which is then separated. The process of precipitation may be proceeded by the process of reduction or oxidation and by the separation of the old impurities. It is characterised in that a medium containing heavy metals - with dominant amounts of chromium and/or iron and/or zinc and/or cadmium and/or nickel - is treated with a basic precipitating agent, preferably with phosphoric (V) acid salts of alkaline metals, or better with phosphoric (V) acid salts of alkaline metals and/or a strong inorganic base. The poorly-soluble deposit of heavy metal compounds is separated from the solution remaining after the deposit precipitation and are subjected to multigrade and multistage processes of refining. The deposit is purified in at least two stages of treatment with an acid and/or a mixture of acids, preferably a strong mineral acid and/or a mixture of strong mineral acids. Particular stages of deposit refining are separated with the operations of physical-and-chemical or chemical purification of solutions obtained at these purification stages. Substances enhancing isolation of organic compounds from the obtained solution or solutions are added before any stage or stages of deposit purification. The substances are selected from the group comprising deflocculation agents, strong electrolytes, polyelectrolytes or adsorbents. The solution remaining after the separation of the poorly-soluble deposit of heavy metal compounds is treated with agents that result in gradual removal of its components that are not heavy metal compounds. The agents are selected from the group comprising: oxides and hydroxides of alkaline metals and/or alkaline earths, soluble salts of alkaline metals and/or alkaline earths and/or light metals and/or iron salts, at least medium-strength acids and/or their salts and/or their anhydrides, gas precursors of acids or bases, elements from group VI and the main group VII in elemental state or their combinations, organic bases and/or their precursors, primary, secondary and tertiary amines and/or their salts, quaternary ammonia compounds, a solution of hydrogen peroxide. Then, the created combinations or deposits are separated physically in each stage.